FUCK

In ancient England , people could not have sex without consent from the King.
When people wanted to have a child, they had to solicit a permission to the monarchy, in turn they would supply a plaque to hang on their door when they had sexual relations.
The plaque read … "Fornication Under Consent of the King" (F.U.C.K).
This is the origin of the word.
Fornication Under Consent of the King (F.U.C.K)